| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical wavelength multiplex system which suppresses dispersion among channels when the multistage repeating of an optical wavelength multiplex signal is executed by using an optical direct amplifier and which is stable by eliminating the deviation of channel levels by means of the automatic gain equalization of the optical direct amplifier through the use of a waveguide optical filter. SOLUTION: The signal which is optical wavelength-multiplexed by a star coupler 2 is collectively amplified in the direct amplifier 3. At that time the deviation occurs in the output levels of the respective channels by the gain wavelength dependency of the amplifier 3. The respective channels are inputted to an MZ waveguide optical filter 5 and are branched in an optical coupler 6. One is transmitted to a transmission line and the other is branched into two in an optical coupler 7. Optical BPF 8 and 9 extract the channels λ1 and λn of the shortest wavelength and the longest wavelength. The voltage of the electrode of the MZ waveguide optical filter 5 is controlled by a control circuit 13 by a difference between electric signals obtained by converting λ1 and λn into electric signals in photoelectric conversion circuits 10 and 11 by a detection circuit 12. Then, the optical amplifier 3 is gain-equalized so that the difference becomes zero by adjusting the inclination of an optical filter characteristic. |
